Controlling laser polarization

Abstract

A laser polarization control apparatus includes a polarization modifying device and a controller. The polarization modifying device receives a laser beam and modifies the polarization of the laser beam. The controller adjusts an input to the polarization modifying device in order to control modification of the polarization of the laser beam based on alignment of a structure to be processed by the laser beam. The polarization modifying device is configured for incorporation into a laser processing system that produces the laser beam received by the polarization modifying device and that focuses the laser beam modified by the polarization modifying device onto a workpiece that includes the structure to be processed by the laser beam. An analyzer tool receives the laser beam modified by the polarization modification device and measures the modification of the polarization of the laser beam by the polarization modification device. A plurality of inputs are applied to the polarization modifying device to control modification of the polarization of the laser beam, and the laser beam modified by the polarization modification device is analyzed using the analyzer tool in order to measure modification of the polarization of the laser beam by the polarization modification device. The relationship between the inputs to the polarization control device and the modification of the polarization of the laser beam is stored.

What is claimed is:  
     
       1. A method of laser processing of a structure comprising: 
       providing a structure to be processed;  
       providing a laser processing system that produces an elliptically or linearly polarized laser beam;  
       determining an orientation of the structure and the polarized laser beam relative to each other such that processing of the structure by the polarized laser beam occurs within a processing energy window that is larger than processing energy windows corresponding to at least some other orientations of the structure and the polarized laser beam relative to each other;  
       processing the structure by focusing the polarized laser beam onto the structure, the structure and the polarized laser beam being at the determined orientation relative to each other.  
     
     
       2. The method of  claim 1  wherein the polarized laser beam is an elliptically polarized laser beam. 
     
     
       3. The method of  claim 1  wherein the polarized laser beam is a linearly polarized laser beam. 
     
     
       4. The method of  claim 1  wherein the determined orientation is parallel with the polarized laser beam. 
     
     
       5. The method of  claim 1  wherein the determined orientation is perpendicular to the polarized laser beam. 
     
     
       6. The method of  claim 1  wherein the laser processing system is configured for cutting links in a semiconductor device, and wherein the structure to be processed by the laser beam is a link. 
     
     
       7. The method of  claim 1  further comprising the steps of providing, in the laser processing system, an analyzer tool arranged to receive the polarized laser beam, the analyzer tool being configured to analyze the polarization of the laser beam. 
     
     
       8. The method of  claim 1  further comprising the step of removing the analyzer tool from the laser processing system. 
     
     
       9. The method of  claim 7  wherein the step of analyzing the polarization of the laser beam is performed at a point of manufacture of the laser processing system. 
     
     
       10. The method of  claim 7  wherein the step of analyzing the polarization of the laser beam is performed at a point of installation of the polarization modifying device into the laser processing system. 
     
     
       11. A laser polarization control apparatus comprising: 
       a polarization modifying device configured to receive a laser beam and to modify the polarization of the laser beam; and  
       a controller, connected to the polarization modifying device, configured to adjust an input to the polarization modifying device in order to control modification of the polarization of the laser beam based on alignment of a structure to be processed by the laser beam;  
       the polarization modifying device being configured for incorporation into a laser processing system that produces the laser beam received by the polarization modifying device and that focuses the laser beam modified by the polarization modifying device onto a workpiece that includes the structure to be processed by the laser beam;  
       wherein the controller is configured to adjust the input to the polarization modifying device so as to cause the structure and the polarized laser beam to be at an orientation relative to each other such that processing of the structure by the polarized laser beam occurs within a processing energy window that is larger than processing energy windows corresponding to at least some other orientations of the structure and the polarized laser beam relative to each other.  
     
     
       12. The laser polarization control apparatus of  claim 11  wherein the laser beam modified by the polarization modifying device is elliptically polarized. 
     
     
       13. The laser polarization control apparatus of  claim 11  wherein the laser beam modified by the polarization modifying device is linearly polarized. 
     
     
       14. The laser polarization control apparatus of  claim 11  wherein the polarization modifying device comprises a liquid crystal variable retarder. 
     
     
       15. The laser polarization control apparatus of  claim 11  wherein the polarization modifying device is configured to modify the polarization of the laser beam by rotating the polarization of the laser beam. 
     
     
       16. The laser polarization control apparatus of  claim 11  wherein the controller is configured to adjust the input to the polarization modifying device so as to cause the polarization of the laser beam to be rotated to correspond with the alignment of the structure to be processed by the laser beam. 
     
     
       17. The laser polarization control apparatus of  claim 11  further comprising a polarizing beamsplitter arranged to process the laser beam to be received by the polarization modifying device to ensure that the laser beam is linearly polarized in a predetermined direction. 
     
     
       18. The laser polarization control apparatus of  claim 11  further comprising a processor programmed to control how the controller adjusts the input to the polarization modifying device, based on stored information specifying alignment of structures to be processed by the laser beam. 
     
     
       19. The laser polarization control apparatus of  claim 11  further comprising an analyzer tool arranged to receive the laser beam modified by the polarization modification device, the analyzer tool being configured to measure the modification of the polarization of the laser beam by the polarization modification device. 
     
     
       20. The laser polarization control apparatus of  claim 19  wherein the analyzer tool is removably insertable into the laser processing system.